Coded light refers to techniques whereby data, such as a Coded Light Identifier (CL ID), is embedded in the light emitted by a light source such as an everyday luminaire. The light typically comprises both a visible illumination contribution for illuminating a target environment such as room (typically the primary purpose of the light), and an embedded signal for providing information into the environment. To do this, the light is modulated at a certain modulation frequency or frequencies, preferably a high enough frequency so as to be beyond human perception and therefore not affecting the primary illumination function. In some cases, a coded light emitter might not have an illumination function at all. In that case, visible light or invisible infra-red light can be used as the medium for transmitting information.
In some of the simplest cases, the signal may comprise a single waveform or even a single tone modulated into the light from a given luminaire. The light emitted by each of a plurality of luminaires may be modulated with a different respective modulation frequency that is unique amongst those luminaires, and the modulation frequency can then serve as an identifier of the luminaire or its light. For example this can be used in a commissioning phase to identify the contribution from each luminaire, or during operation can be used to identify a luminaire in order to control it remotely (e.g. via an RF back channel). In another example, the identification can be used for navigation or other location-based functionality, by mapping the identifier to a known location of a luminaire or information associated with the location.
In other cases, a signal comprising more complex data may be embedded in the light. For example using amplitude keying the amplitude of the light may be varied to encode data, e.g. using high and low levels to represent bits or using a more complex modulation scheme to represent different symbols. Or using frequency keying, a given luminaire is operable to emit on two (or more) different modulation frequencies and to transmit data bits (or more generally symbols) by switching between the different modulation frequencies.
Using Visible Light Communication (VLC) techniques based on coded light, it is possible to provide location awareness, whereby a user device, such as a smart phone or tablet computer, can be located in a building or other environment based on camera images of the luminaires in the ceiling captured by the user device. These luminaires are identified through a CL ID, also referred to herein as a VLC code. With proper configuration, it is possible to determine the location within centimeter accuracy. Location awareness has many applications, and can be used for example to provide information about the item present in a particular location in a shop or museum, or to show the way to a particular item.
The usual way a VLC Indoor Positioning system is configured is with each of the luminaires having a respective unique VLC code that is sent through VLC. These luminaires are installed randomly, and then commissioned in the “commissioning” phase after they have been installed. The commissioning stage involves generating a list in which, for each of the installed luminaires, its respective VLC code is listed in association with an identifier of the location in the building of the luminaire. This list is stored in a database that can then be used, when a code is identified by the mobile device, to retrieve its associated location. Using existing techniques, this is essentially a manual process whereby a technician uses their user device to detect the VLC code emitted by each luminaire at each location, and updates the database to associate that VLC code with that location, one-by-one.
After the database has been populated, some or all of the data may be verified, by a technician going back over the luminaires with their device. For example, US2015/0003836 describes a system in which positions on a map, displayed on a touchscreen, individually correspond to rectangular squares in a grid of lighting fixtures. A control unit can operate in a correction mode. In the correction mode, when identification information is received from a lighting fixture, its recorded location, e.g. grid position (8-G), is displayed on the map. The user can then correct the location, if they can see it is incorrect, by touching the corrected location, e.g. (8-F).